Seriously, however, if we are talking about shock absorbers (rather than struts), the old “bounce test” is fairly reliable. Push very hard on one corner of the car. If it does not stop bouncing within one down motion and one up motion, then the shock absorber on that wheel is shot. Shocks are always replaced in an axle set (both front shocks, or both rear shocks, or even better–all 4 at the same time).

Without even doing the bounce test, if you experience continued bouncing of the car after it has gone over a bump–or even over a dip in the road–then the shock absorbers are due for replacement. You should have a ride that feels “in control”, rather than a ride consisting of constant up and down motions.

A car with no shocks at all would bounce down the road. When you hit a bump you compress the spring and the spring rebounds making the car bounce. The shock allows the wheel to move but limits the rebounding so there is no bounce.

Therefore you test to detect bounce. Push down on each corner of the car and try to get it rocking a bit, then release your pressure and see it the car quickly comes to rest. If it continues to bounce up and down a bit, then the shock is bad.

You can also feel if one side of the front or back is significantly easier to push down than the other side. The easier side has a weakened shock.

Sometimes you can visually see fluid leaking from a bad shock when the car is on a lift.

I’d bet that if you could tell us more, we might be able to give more complete answers.

For starter’s Make model and year of car. How about the number of miles. Why do you ask the question? Do you think it might need them? Why? Have they ever been replaced? Has someone suggested you need to replace them (like your local fast lube place?)